Past Mistakes
by Yaminoko-Jeichan
Summary: Everyone knows that Koenma made a terrible mistake when he hired Sensui, but he's not the only Spirit World prince who made mistakes. What happens when one of his father, King Yama's mistakes come back to haunt the world?
1. Chapter 1

_Disclaimer: Don't own show._

Prologue: King Yama's POV

The first clue had been the lightning flashing across the sky—red, not yellow like it should be, and the second had been the heavy shadows slowly overpowering the light, choking it unto submission. And now, as I stared expressionlessly from my desk at the stormy skies, I saw the third and final clue: the glow from the full moon faded into pure black, deeper than the surrounding sky, with a blood red outline the only thing to show that it was still there.

He was back; I knew it—the prophecy made so long ago was set to be fulfilled and soon. There was nothing I could do now except wait and hope things wouldn't turn out as foretold. I had clung desperately to that hope for countless millennia, always waiting and struggling to forget what I knew that no one else did—the prophesized one's true identity; but I never succeeded, the guilt was almost too much to bear.

"Father? You wanted to see me?" My son walked up to me still using his living world form instead of his Spirit World one—in defiance.

"You've noticed the strange happenings in the living world, haven't you?"

"Yes. Hectic weather patterns—a spontaneous solar eclipse yesterday." My son replied and then furrowed his brows as he stared at the sky. "But it's nothing compared to what's going on here."

"…."

"Father, what's happening?"

"The beginning of a prophecy's fulfillment." I answered sighing and then handed my son a sealed folder that I had kept hidden for millennia waiting for this day.

"Father, this folder…I've never seen…."

"Take it to the Living World, to your Spirit Detective, and read it there. I need to visit someone and warn them."

"About what?"

"You'll find out soon enough."

"But father…." My son began, but I left quickly, opening a portal to where I needed to go, and closing it as soon as I entered so that no one could follow.

_Short, I know, but tell me what you think of it anyway._


	2. Chapter 2

Past Mistakes:

Chapter two:

After receiving the file from his father, Koenma hurried to the human realm, his heart pounding as he remembered the look on his father's face—it was a look of pure fear and…and a desolate helplessness. He never before saw his father like that, and it tore at his own security.

Reaching Genkai's, the Spirit World prince was greeted with a certain eagerness by the Spirit Detective and company—everyone was worried about the bizarre events occurring in the human realm for the past few days. Everything was toned down compared to the spirit world, but it still worried the Spirit Detective and others.

"Koenma, did you find out anything about what's going on from that old man of yours?" Yusuke asked the moment the Spirit World prince stepped through the sliding temple door.

"He gave me this file," He held up the folder for the detective to see. "And left…he looked pretty wound up from what's been happening…."

"It must be something serious then." Yusuke looked at the folder in Koenma's hand, not really wanting to read. "So what does the file say? Is it some demon or something that's causing this?"

"I haven't read it, I came as soon as my father handed me this. But I'll read it now." The brown haired prince opened the file, grimacing when a single sheet of paper came out.

"What the…? A single sheet of paper is supposed to explain what's been happening? Hell!"

Koenma ignored the Spirit Detective as he read the paper silently, growing pale with each word.

"Koenma? What's wrong? What does the paper say?"

"I…the prophecy…I can't…."

"Koenma?"

"This paper is about a prophecy made long ago, about a demon called the Slayer. It's…."

"And who is this demon? What's the big deal? Is he really dangerous?" Yusuke grabbed the paper from the prince, grimacing when the paper didn't explain anything specific about the demon. "What's the big deal? There's nothing explaining who this Slayer person is. If he's such a big deal why isn't anything written about him?"

Koenma remained silent in thought for a moment, and then started to answer the Detective when someone else spoke up.

Green eyes shimmering cold, Kurama stepped into the room in time to hear what the Detective had said about the Slayer, hiding his shock with his stoic mask.

"Because there's not much known about the Slayer. He lived millennia ago, and the humans who knew of him are all dead."

"Kurama, you know of this demon in this prophecy?" Yusuke asked expression bewildered and curious. "Why didn't you say so before? And where have you been for the past few days?"

"I've been in Demon World trying to get some information. I didn't say anything about the Slayer because I didn't know it was about him before this." The fox-demon replied, eyeing the paper in the Yusuke's hands wearily. "And I'm still hoping it isn't about him."

"Why…?"

"The Slayer…he's a demon all those in demon world feared and still fear. No one knows for sure if he's dead or alive, but they do know of the prophecy whispered by his followers." Kurama paused; face darkening as he thought of his words.

"That's not much info. He must be powerful if demon's fear him so much, but how powerful is he? I bet I can take him on no problem."

"That's bold, since no one who ever faced the Slayer lived to talk about it. That's one reason why not much is known about him." A new voice supplied, and in stepped a spiky-haired red eyed demon.

"Hiei! I thought you were in Demon World with Mukuro."

"Hn."

"As difficult as ever." Yusuke turned back to Kurama. "Well, what is known about this demon?"


	3. Chapter 3

**Past Mistakes**

**Chapter Three:**

**King Yama's POV:**

Nearly twenty minutes after giving my son the file, I approached a castle stronghold, grey stone, shadow-encased, and stared at the towering door blocking the entrance. As massive as I am, this door not only deterred intruders from its size, but also from the powerful aura surrounding it. And these two were just precautions that hardly were needed—the whole castle resided in a realm one needs to know of before they could even hope to enter.

I am one of the select few who know of it—the only one from the outside who can get into this realm.

"King Yama." A high squeaky voice spoke from my left—a winged creature with cat claws and a body like a cat/lizard hybrid fluttered next to me. "Master Karakas has been expecting you. Go right in." The creature turned away as the towering door opened, opening inward toward the dark interior.

On my first step into the front corridor of the castle, the torches on the walls lit up, killing the blanket of shadows that had decorated the corridor moments before. Knowing my way around, I headed toward the main room of the castle, not expecting any greeting until I got to the main hall.

"Yama." Came a voice so cold, so indifferent, but I detected a flicker of invite in the tone. "I've wondered when you would show."

"Karakas." I stopped walking as the voice's owner stepped from the part of the hall the light hadn't yet reached.

Long, white-blond hair falling past broad shoulders, pulled behind so that it only touched his back, Karakas stepped closer to me until he stopped five feet away. His fiery-red eyes studied me for a moment before closing.

"So the time's come at last."

"Yes it has."

"You remember your promise, don't you? Do you still plan on keeping it?" Karakas drawled carelessly, as though speaking trifle questions though I knew differently.

"Yes, I will not go back on my word. I promised you protection and I will give you it." I paused and looked him directly in the eye. "Now I want you to promise you will not seek him out, you will not seek him out for revenge."

"Why would I seek out someone who wants to kill me? You know as well as I, that the Slayer swore to hunt me down and quench his sword in my blood. His rage for me is uncanny; it was a miracle I escaped from him the first and only time I met him."

"You abandoned your son to escape, that wasn't a miracle."

Suddenly Karakas glared at me, indignation shining in his scarlet eyes.

"I did not abandon Seisol, the Slayer kidnapped him from me when I encountered him; I could not save my son."

"Did you even try?"

"Yes I did. Why do you think I have this scar?" Karakas pointed to a long scar on the left side of his face going from his ear to his lips. "He gave it to me when I tried to take back Seisol."

A few moments of uncomfortable silence passed between us before he spoke again.

"I never found out why the Slayer specifically targeted me—did you know he was searching for me before he met me? He described my name and appearance perfectly to those he questioned—I have yet to figure out how he could know me when we met only once."

I remained silent to this, beating down the guilt filling my gut, bursting for release. _'If he only knew…what would he think if he knew _who_ it had really been?'_

"Have you discovered anything knew about the Slayer?"

"No, but I have given a mission to my son to give to the most recent Spirit Detective he trained."

"Would this Spirit Detective be the one descendant from the demon Raizen?"

"Yes…how do you know about that? You're supposed to keep to this realm, how have you gain information about the outside?"

"I've sent out a few…spies to the outside. Plus my mate can freely go as she pleases—No one, except me and you, knows who she is or her appearance."

'_There is one,'_ I wanted to blurt. _'And if he knew _she_ was _your_ mate now, he would have even more incentive to hunt you down.'_

"As I said, I came here for your promise not to interfere with my plan with dealing with the Slayer. If you promise not to leave the safety of this realm, even for a second, I will leave now so you can get back to whatever business you have going." I nodded toward the entrance into the main room, trying hard not to listen to the indistinct sounds coming from behind the door.

"Heh, yes I do have something going on in there—not what you think though, not that you'll believe that." Karakas chuckled, "You'll never stop your assumptions about lust demons, will you? Anyway, you have my word that I won't leave my roost until after you deal with the Slayer—and I will leave only if you manage to capture and subdue that demon."

With that he turned and disappeared down the corridor, and I turned to walk through the gate once more. Before I left the realm I stared at the graying sky, shuddering when the image of a male with ice-blue eyes and brown hair flashed through my mind.

"Hitoru, why did you have to stray so far? And why do you have to return now?"

**A/N: End Chapter, please review.**


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